An Ethernet interface, such as a 10/100/1000 BaseT Ethernet, has traditionally been treated as intra-building (indoor only) interface much like a RS-232 interface. Power over Ethernet (PoE) was developed to provide electrical power and network data capability over standard Ethernet cabling to locations where AC (alternating current) power would be inconvenient, expensive, or otherwise infeasible to install. Even in situations where AC power is feasible, PoE offers additional advantages. PoE is simple to set up and because it operates at low voltage (typically Direct Current (DC) voltage of approximately 48V), and typically does not require an electrician to install. Another benefit is that data and power are combined on a single cable, which reduces cabling requirements and complexity. In most PoE installations, existing network cabling infrastructure can be used. The flexibility that PoE offers by combining network signal and power into a single Ethernet cable makes it highly desirable for many communication applications.
A typical PoE installation uses two twisted pairs of cable in a standard TIA-568B CATS/6 RJ-45 Ethernet cable connection to carry Ethernet data and DC power to a PoE enabled device. The Ethernet interface was not intended for deployment in outside (outdoor) plant environments where the interface may be exposed to high-energy lightning and power fault events. Safety organizations, such as Underwriters Laboratories (UL), and corresponding electrical safety standards have not provided protection requirements or guidelines for Ethernet interfaces that are exposed to outdoor faults. As a result, placing products having only indoor Ethernet interface protection in an outdoor environment is generally undesirable. High-energy lightning and power faults are capable of causing significant product damage and also pose electrical safety and fire hazards.
Further, standards such as Telcordia GR-1089-CORE, and Institute of Electrical and Electronics Engineers (I.E.E.E.) Ethernet specifications assume limited exposure to mild electrical transients. The mild electrical transients typically encountered by an indoor Ethernet cable can be induced from adjacent wiring and/or electrical equipment (e.g., motors, copiers, elevators, medical equipment, etc.). Generally, the existing protection schemes for an indoor Ethernet interface typically comprises transient suppression circuits designed to handle small intra-building electrical transients. Thus, the use of Ethernet cables and interfaces has typically been limited to indoor environments.
Service providers have undertaken initiatives that expose either the service provider's Ethernet interfaces or the customer's Ethernet interfaces to an outdoor environment. Hence, Ethernet equipment may be damaged from exposure to a high-energy electrical impulse, such as lightning (either induced or via a ground potential rise (GPR)) or an alternating current (AC) power fault. Not only is such an exposure a violation of one or more safety listings, but the provider's placement of equipment may cause loss of service, damage to the equipment, and/or injury to a user.
There exist many conventional surge protection systems for protecting various products from high voltage and/or current surges. However, many such protection systems would degrade the performance of an Ethernet signal such that the requirements of applicable Ethernet standards, such as I.E.E.E. 802.3, would be violated. In this regard, I.E.E.E. 802.3 sets limits on both the insertion loss and return loss of the Ethernet interface at frequencies up to 100 megaHertz (MHz). Many protection schemes, having been developed for much lower bandwidth circuits, are therefore not suitable for Ethernet.
Moreover, there is a need for a surge protection system that protects equipment coupled to an outdoor Ethernet cable. It would be desirable for such a surge protection system to be compliant with applicable Ethernet transmission standards, such as I.E.E.E. 802.3.